CascadiaPHP 2024

The SplStack class

(PHP 5 >= 5.3.0, PHP 7, PHP 8)

Introduction

The SplStack class provides the main functionalities of a stack implemented using a doubly linked list by setting the iterator mode to SplDoublyLinkedList::IT_MODE_LIFO.

Examples

Example #1 SplStack example

<?php
$q
= new SplStack();
$q[] = 1;
$q[] = 2;
$q[] = 3;
foreach (
$q as $elem) {
echo
$elem."\n";
}
?>

The above example will output:

3
2
1

add a note

User Contributed Notes 3 notes

up
41
lsroudi at gmail dot com
10 years ago
the SplStack is simply a SplDoublyLinkedList with an iteration mode IT_MODE_LIFO and IT_MODE_KEEP
up
8
lincoln dot du dot j at gmail dot com
7 years ago
<?php
//SplStack Mode is LIFO (Last In First Out)

$q = new SplStack();

$q[] = 1;
$q[] = 2;
$q[] = 3;
$q->push(4);
$q->add(4,5);

$q->rewind();
while(
$q->valid()){
echo
$q->current(),"\n";
$q->next();
}
?>

Output
5
4
3
2
1
up
-12
daryledesilva at gmail dot com
4 years ago
<?php

// Exercise: Implement Queue using Stacks

class MyQueue {
protected
$queue;

/**
* Initialize your data structure here.
*/
function __construct() {
$this->queue = new \SplStack;
}

/**
* Push element x to the back of queue.
* @param Integer $x
* @return NULL
*/
function push($x) {
$this->queue->push($x);
}

/**
* Removes the element from in front of queue and returns that element.
* @return Integer
*/
function pop() {
$length = count($this->queue);
$temp = [];
while(!
$this->queue->isEmpty()){
$rv = $this->queue->pop();
if(!
$this->queue->isEmpty()){
$temp[] = $rv;
}
}
for(
$i = count($temp)-1; $i >= 0; $i--){
$this->queue->push($temp[$i]);
}
return
$rv;
}

/**
* Get the front element.
* @return Integer
*/
function peek() {
return
$this->queue->bottom();
}

/**
* Returns whether the queue is empty.
* @return Boolean
*/
function empty() {
return
$this->queue->isEmpty();
}
}

/**
* Your MyQueue object will be instantiated and called as such:
* $obj = MyQueue();
* $obj->push($x);
* $ret_2 = $obj->pop();
* $ret_3 = $obj->peek();
* $ret_4 = $obj->empty();
*/
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